What Side Effects Should I Expect After Injections of Botox?

Since Botox is a very safe medication if used properly, there are very few side effects.  You may experience a small bruise at the injection site and very rarely, a headache or droopy eyelid.  It will take about 10 days to see the full effect of your Botox treatment.

Botox is very well tolerated and side effects are uncommon. The most common side effects, which aren't common at all, are a headache and very mild bruising. There may also be temporary redness or swelling. Very uncommonly, particularly if not treated by an expert such as a dermatologist, there is the risk of an eyebrow or eyelid drooping for a few weeks; there is also the uncommon risk of a "spock brow."  Dr. Benjamin Barankin, Toronto Dermatology Centre.